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Banigan EJ, Tang W, van den Berg AA, Stocsits RR, Wutz G, Brandão HB, Busslinger GA, Peters JM, Mirny LA. Transcription shapes 3D chromatin organization by interacting with loop extrusion. Proc Natl Acad Sci U S A 2023; 120:e2210480120. [PMID: 36897969 PMCID: PMC10089175 DOI: 10.1073/pnas.2210480120] [Citation(s) in RCA: 49] [Impact Index Per Article: 49.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/17/2022] [Accepted: 12/03/2022] [Indexed: 03/12/2023] Open
Abstract
Cohesin folds mammalian interphase chromosomes by extruding the chromatin fiber into numerous loops. "Loop extrusion" can be impeded by chromatin-bound factors, such as CTCF, which generates characteristic and functional chromatin organization patterns. It has been proposed that transcription relocalizes or interferes with cohesin and that active promoters are cohesin loading sites. However, the effects of transcription on cohesin have not been reconciled with observations of active extrusion by cohesin. To determine how transcription modulates extrusion, we studied mouse cells in which we could alter cohesin abundance, dynamics, and localization by genetic "knockouts" of the cohesin regulators CTCF and Wapl. Through Hi-C experiments, we discovered intricate, cohesin-dependent contact patterns near active genes. Chromatin organization around active genes exhibited hallmarks of interactions between transcribing RNA polymerases (RNAPs) and extruding cohesins. These observations could be reproduced by polymer simulations in which RNAPs were moving barriers to extrusion that obstructed, slowed, and pushed cohesins. The simulations predicted that preferential loading of cohesin at promoters is inconsistent with our experimental data. Additional ChIP-seq experiments showed that the putative cohesin loader Nipbl is not predominantly enriched at promoters. Therefore, we propose that cohesin is not preferentially loaded at promoters and that the barrier function of RNAP accounts for cohesin accumulation at active promoters. Altogether, we find that RNAP is an extrusion barrier that is not stationary, but rather, translocates and relocalizes cohesin. Loop extrusion and transcription might interact to dynamically generate and maintain gene interactions with regulatory elements and shape functional genomic organization.
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Affiliation(s)
- Edward J. Banigan
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Wen Tang
- Research Institute of Molecular Pathology, Vienna BioCenter1030Vienna, Austria
| | - Aafke A. van den Berg
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA02139
| | - Roman R. Stocsits
- Research Institute of Molecular Pathology, Vienna BioCenter1030Vienna, Austria
| | - Gordana Wutz
- Research Institute of Molecular Pathology, Vienna BioCenter1030Vienna, Austria
| | - Hugo B. Brandão
- Graduate Program in Biophysics, Harvard University, Cambridge, MA02138
- Department of Biological Engineering, Massachusetts Institute of Technology, Cambridge, MA02139
- The Broad Institute of MIT and Harvard, Cambridge, MA02142
| | - Georg A. Busslinger
- Research Institute of Molecular Pathology, Vienna BioCenter1030Vienna, Austria
- Research Center for Molecular Medicine of the Austrian Academy of Sciences, Vienna1090, Austria
- Division of Gastroenterology and Hepatology, Department of Internal Medicine III, Medical University of Vienna, Vienna1090, Austria
| | - Jan-Michael Peters
- Research Institute of Molecular Pathology, Vienna BioCenter1030Vienna, Austria
| | - Leonid A. Mirny
- Department of Physics, Massachusetts Institute of Technology, Cambridge, MA02139
- Institute for Medical Engineering and Science, Massachusetts Institute of Technology, Cambridge, MA02139
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Qui-Minet ZN, Davoult D, Grall J, Delaunay C, Six C, Cariou T, Martin S. Physiology of maerl algae: Comparison of inter- and intraspecies variations. JOURNAL OF PHYCOLOGY 2021; 57:831-848. [PMID: 33316844 DOI: 10.1111/jpy.13119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/17/2020] [Revised: 10/09/2020] [Accepted: 11/08/2020] [Indexed: 06/12/2023]
Abstract
Free-living red coralline algae play an important role in the carbon and carbonate cycles of coastal environments. In this study, we examined the physiology of free-living coralline algae-forming maerl beds in the Bay of Brest (Brittany, France), where Lithothamnion corallioides is the dominant maerl (i.e., rhodolith) species. Phymatolithon calcareum and Lithophyllum incrustans are also present (in lower abundances) at a specific site in the bay. We aimed to assess how maerl physiology is affected by seasonality and/or local environmental variations at the inter- and intraspecific levels. Physiological measurements (respiration, photosynthetic, and calcification rates) were performed using incubation chambers in winter and summer to compare (1) the dominant maerl species at three sites and (2) three coexisting maerl species at one site. Comparison of the three coexisting maerl species suggests that L. corallioides is the best adapted to the current environmental conditions in the Bay of Brest, because this species is the most robust to dissolution in the dark in winter and has the highest calcification efficiency in the light. Comparisons of L. corallioides metabolic rates between stations showed that morphological variations within this species are the main factor affecting its photosynthetic and calcification rates. Environmental factors such as freshwater inputs also affect its calcification rates in the dark. In addition to interspecies variation in maerl physiology, there were intraspecific variations associated with direct (water physico-chemistry) or indirect (morphology) local environmental conditions. This study demonstrates the plasticity of maerl physiology in response to environmental changes, which is fundamental for maerl persistence.
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Affiliation(s)
- Zujaila Nohemy Qui-Minet
- CNRS, UMR 7144 Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff, Sorbonne Université, Place Georges Teissier, 29688, Roscoff Cedex, France
| | - Dominique Davoult
- CNRS, UMR 7144 Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff, Sorbonne Université, Place Georges Teissier, 29688, Roscoff Cedex, France
| | - Jacques Grall
- IUEM, Université de Bretagne Occidentale, Place Nicolas Copernic, 29280, Plouzané, France
| | - Coralie Delaunay
- CNRS, UMR 7144 Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff, Sorbonne Université, Place Georges Teissier, 29688, Roscoff Cedex, France
| | - Christophe Six
- CNRS, UMR 7144 Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff, Sorbonne Université, Place Georges Teissier, 29688, Roscoff Cedex, France
| | - Thierry Cariou
- CNRS, Fédération de Recherche FR2424, Station Biologique de Roscoff, Sorbonne Université, Place Georges Teissier, 29680, Roscoff, France
| | - Sophie Martin
- CNRS, UMR 7144 Adaptation et Diversité en Milieu Marin, Station Biologique de Roscoff, Sorbonne Université, Place Georges Teissier, 29688, Roscoff Cedex, France
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3
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Kirstein N, Buschle A, Wu X, Krebs S, Blum H, Kremmer E, Vorberg IM, Hammerschmidt W, Lacroix L, Hyrien O, Audit B, Schepers A. Human ORC/MCM density is low in active genes and correlates with replication time but does not delimit initiation zones. eLife 2021; 10:62161. [PMID: 33683199 PMCID: PMC7993996 DOI: 10.7554/elife.62161] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2020] [Accepted: 03/05/2021] [Indexed: 12/22/2022] Open
Abstract
Eukaryotic DNA replication initiates during S phase from origins that have been licensed in the preceding G1 phase. Here, we compare ChIP-seq profiles of the licensing factors Orc2, Orc3, Mcm3, and Mcm7 with gene expression, replication timing, and fork directionality profiles obtained by RNA-seq, Repli-seq, and OK-seq. Both, the origin recognition complex (ORC) and the minichromosome maintenance complex (MCM) are significantly and homogeneously depleted from transcribed genes, enriched at gene promoters, and more abundant in early- than in late-replicating domains. Surprisingly, after controlling these variables, no difference in ORC/MCM density is detected between initiation zones, termination zones, unidirectionally replicating regions, and randomly replicating regions. Therefore, ORC/MCM density correlates with replication timing but does not solely regulate the probability of replication initiation. Interestingly, H4K20me3, a histone modification proposed to facilitate late origin licensing, was enriched in late-replicating initiation zones and gene deserts of stochastic replication fork direction. We discuss potential mechanisms specifying when and where replication initiates in human cells.
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Affiliation(s)
- Nina Kirstein
- Research Unit Gene Vectors, Helmholtz Zentrum München (GmbH), German Research Center for Environmental Health, Munich, Germany
| | - Alexander Buschle
- Research Unit Gene Vectors, Helmholtz Zentrum München (GmbH), German Research Center for Environmental Health and German Center for Infection Research (DZIF), Munich, Germany
| | - Xia Wu
- Institut de Biologie de l'ENS (IBENS), Département de Biologie, Ecole Normale Supérieure, CNRS, Inserm, PSL Research University, Paris, France
| | - Stefan Krebs
- Laboratory for Functional Genome Analysis (LAFUGA), Gene Center of the Ludwig-Maximilians Universität (LMU) München, Munich, Germany
| | - Helmut Blum
- Laboratory for Functional Genome Analysis (LAFUGA), Gene Center of the Ludwig-Maximilians Universität (LMU) München, Munich, Germany
| | - Elisabeth Kremmer
- Institute for Molecular Immunology, Monoclonal Antibody Core Facility, Helmholtz Zentrum München, German Research Center for Environmental Health (GmbH), Neuherberg, Germany
| | - Ina M Vorberg
- German Center for Neurodegenerative Diseases (DZNE e.V.), Bonn, Germany.,Rheinische Friedrich-Wilhelms-Universität Bonn, Bonn, Germany
| | - Wolfgang Hammerschmidt
- Research Unit Gene Vectors, Helmholtz Zentrum München (GmbH), German Research Center for Environmental Health and German Center for Infection Research (DZIF), Munich, Germany
| | - Laurent Lacroix
- Institut de Biologie de l'ENS (IBENS), Département de Biologie, Ecole Normale Supérieure, CNRS, Inserm, PSL Research University, Paris, France
| | - Olivier Hyrien
- Institut de Biologie de l'ENS (IBENS), Département de Biologie, Ecole Normale Supérieure, CNRS, Inserm, PSL Research University, Paris, France
| | - Benjamin Audit
- Univ Lyon, ENS de Lyon, Univ. Claude Bernard, CNRS, Laboratoire de Physique, 69342 Lyon, France
| | - Aloys Schepers
- Research Unit Gene Vectors, Helmholtz Zentrum München (GmbH), German Research Center for Environmental Health, Munich, Germany
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4
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Saleh MM, Tourigny JP, Zentner GE. Genome-Wide Profiling of Protein-DNA Interactions with Chromatin Endogenous Cleavage and High-Throughput Sequencing (ChEC-Seq ). Methods Mol Biol 2021; 2351:289-303. [PMID: 34382196 DOI: 10.1007/978-1-0716-1597-3_16] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
Interactions between regulatory proteins and specific genomic regions are critical for all chromatin-based processes, including transcription, DNA replication, and DNA repair. Genome-wide mapping of such interactions is most commonly performed with chromatin immunoprecipitation followed by high-throughput sequencing (ChIP-Seq), but a number of orthogonal methods employing targeted enzymatic activity have also been introduced. We previously described a genome-wide implementation of chromatin endogenous cleavage (ChEC-Seq), wherein a protein of interest is fused to micrococcal nuclease (MNase) to enable targeted, calcium-dependent genomic cleavage. Here, we describe the ChEC-Seq protocol for use in budding yeast though it can be used in other organisms in conjunction with appropriate methods for introduction of an MNase fusion protein.
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Affiliation(s)
| | | | - Gabriel E Zentner
- Department of Biology, Indiana University, Bloomington, IN, USA.
- Indiana University Melvin and Bren Simon Comprehensive Cancer Center, Indianapolis, IN, USA.
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5
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Henikoff S, Henikoff JG, Kaya-Okur HS, Ahmad K. Efficient chromatin accessibility mapping in situ by nucleosome-tethered tagmentation. eLife 2020; 9:e63274. [PMID: 33191916 PMCID: PMC7721439 DOI: 10.7554/elife.63274] [Citation(s) in RCA: 59] [Impact Index Per Article: 14.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2020] [Accepted: 11/13/2020] [Indexed: 12/27/2022] Open
Abstract
Chromatin accessibility mapping is a powerful approach to identify potential regulatory elements. A popular example is ATAC-seq, whereby Tn5 transposase inserts sequencing adapters into accessible DNA ('tagmentation'). CUT&Tag is a tagmentation-based epigenomic profiling method in which antibody tethering of Tn5 to a chromatin epitope of interest profiles specific chromatin features in small samples and single cells. Here, we show that by simply modifying the tagmentation conditions for histone H3K4me2 or H3K4me3 CUT&Tag, antibody-tethered tagmentation of accessible DNA sites is redirected to produce chromatin accessibility maps that are indistinguishable from the best ATAC-seq maps. Thus, chromatin accessibility maps can be produced in parallel with CUT&Tag maps of other epitopes with all steps from nuclei to amplified sequencing-ready libraries performed in single PCR tubes in the laboratory or on a home workbench. As H3K4 methylation is produced by transcription at promoters and enhancers, our method identifies transcription-coupled accessible regulatory sites.
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Affiliation(s)
- Steven Henikoff
- Basic Sciences Division Fred Hutchinson Cancer Research CenterSeattleUnited States
- Howard Hughes Medical InstituteSeattleUnited States
| | - Jorja G Henikoff
- Basic Sciences Division Fred Hutchinson Cancer Research CenterSeattleUnited States
| | - Hatice S Kaya-Okur
- Basic Sciences Division Fred Hutchinson Cancer Research CenterSeattleUnited States
| | - Kami Ahmad
- Basic Sciences Division Fred Hutchinson Cancer Research CenterSeattleUnited States
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6
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Pavlaki I, Docquier F, Chernukhin I, Kita G, Gretton S, Clarkson CT, Teif VB, Klenova E. Poly(ADP-ribosyl)ation associated changes in CTCF-chromatin binding and gene expression in breast cells. BIOCHIMICA ET BIOPHYSICA ACTA-GENE REGULATORY MECHANISMS 2018; 1861:718-730. [PMID: 29981477 PMCID: PMC6074063 DOI: 10.1016/j.bbagrm.2018.06.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 01/23/2018] [Revised: 06/23/2018] [Accepted: 06/23/2018] [Indexed: 12/11/2022]
Abstract
CTCF is an evolutionarily conserved and ubiquitously expressed architectural protein regulating a plethora of cellular functions via different molecular mechanisms. CTCF can undergo a number of post-translational modifications which change its properties and functions. One such modifications linked to cancer is poly(ADP-ribosyl)ation (PARylation). The highly PARylated CTCF form has an apparent molecular mass of 180 kDa (referred to as CTCF180), which can be distinguished from hypo- and non-PARylated CTCF with the apparent molecular mass of 130 kDa (referred to as CTCF130). The existing data accumulated so far have been mainly related to CTCF130. However, the properties of CTCF180 are not well understood despite its abundance in a number of primary tissues. In this study we performed ChIP-seq and RNA-seq analyses in human breast cells 226LDM, which display predominantly CTCF130 when proliferating, but CTCF180 upon cell cycle arrest. We observed that in the arrested cells the majority of sites lost CTCF, whereas fewer sites gained CTCF or remain bound (i.e. common sites). The classical CTCF binding motif was found in the lost and common, but not in the gained sites. The changes in CTCF occupancies in the lost and common sites were associated with increased chromatin densities and altered expression from the neighboring genes. Based on these results we propose a model integrating the CTCF130/180 transition with CTCF-DNA binding and gene expression changes. This study also issues an important cautionary note concerning the design and interpretation of any experiments using cells and tissues where CTCF180 may be present.
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Affiliation(s)
- Ioanna Pavlaki
- University of Essex, School of Biological Sciences, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK
| | - France Docquier
- University of Essex, School of Biological Sciences, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK
| | - Igor Chernukhin
- University of Essex, School of Biological Sciences, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK
| | - Georgia Kita
- University of Essex, School of Biological Sciences, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK
| | - Svetlana Gretton
- University of Essex, School of Biological Sciences, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK
| | - Christopher T Clarkson
- University of Essex, School of Biological Sciences, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK
| | - Vladimir B Teif
- University of Essex, School of Biological Sciences, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK.
| | - Elena Klenova
- University of Essex, School of Biological Sciences, Wivenhoe Park, Colchester, Essex CO4 3SQ, UK.
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7
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Cryo-EM structure of a Marseilleviridae virus particle reveals a large internal microassembly. Virology 2018; 516:239-245. [PMID: 29407382 DOI: 10.1016/j.virol.2018.01.021] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Revised: 01/24/2018] [Accepted: 01/25/2018] [Indexed: 02/07/2023]
Abstract
Nucleocytoplasmic large DNA viruses (NCLDVs) blur the line between viruses and cells. Melbournevirus (MelV, family Marseilleviridae) belongs to a new family of NCLDVs. Here we present an electron cryo-microscopy structure of the MelV particle, with the large triangulation number T = 309 constructed by 3080 pseudo-hexagonal capsomers. The most distinct feature of the particle is a large and dense body (LDB) consistently found inside all particles. Electron cryo-tomography of 147 particles shows that the LDB is preferentially located in proximity to the probable lipid bilayer. The LDB is 30 nm in size and its density matches that of a genome/protein complex. The observed LDB reinforces the structural complexity of MelV, setting it apart from other NCLDVs.
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8
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Abstract
Chromosomal translocations are a hallmark of cancer. Unraveling the molecular mechanism of these rare genetic events requires a clear distinction between correlative and causative risk-determinants, where technical and analytical issues can be excluded. To meet this goal, we performed in-depth analyses of publicly available genome-wide datasets. In contrast to several recent reports, we demonstrate that chromosomal translocation risk is causally unrelated to promoter stalling (Spt5), transcriptional activity, or off-targeting activity of the activation-induced cytidine deaminase. Rather, an open chromatin configuration, which is not promoter-specific, explained the elevated translocation risk of promoter regions. Furthermore, the fact that gene size directly correlates with the translocation risk in mice and human cancers further demonstrated the general irrelevance of promoter-specific activities. Interestingly, a subset of translocations observed in cancer patients likely initiates from double-strand breaks induced by an access-independent process. Together, these unexpected and novel insights are fundamental in understanding the origin of chromosome translocations and, consequently, cancer.
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9
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Kasinathan S, Orsi GA, Zentner GE, Ahmad K, Henikoff S. High-resolution mapping of transcription factor binding sites on native chromatin. Nat Methods 2013; 11:203-9. [PMID: 24336359 PMCID: PMC3929178 DOI: 10.1038/nmeth.2766] [Citation(s) in RCA: 134] [Impact Index Per Article: 12.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2013] [Accepted: 10/28/2013] [Indexed: 12/20/2022]
Abstract
Sequence-specific DNA-binding proteins including transcription factors (TFs) are key determinants of gene regulation and chromatin architecture. Formaldehyde cross-linking and sonication followed by Chromatin ImmunoPrecipitation (X-ChIP) is widely used for profiling of TF binding, but is limited by low resolution and poor specificity and sensitivity. We present a simple protocol that starts with micrococcal nuclease-digested uncross-linked chromatin and is followed by affinity purification of TFs and paired-end sequencing. The resulting ORGANIC (Occupied Regions of Genomes from Affinity-purified Naturally Isolated Chromatin) profiles of Saccharomyces cerevisiae Abf1 and Reb1 provide highly accurate base-pair resolution maps that are not biased toward accessible chromatin, and do not require input normalization. We also demonstrate the high specificity of our method when applied to larger genomes by profiling Drosophila melanogaster GAGA Factor and Pipsqueak. Our results suggest that ORGANIC profiling is a widely applicable high-resolution method for sensitive and specific profiling of direct protein-DNA interactions.
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Affiliation(s)
- Sivakanthan Kasinathan
- 1] Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA. [2] Medical Scientist Training Program, University of Washington School of Medicine, Seattle, Washington, USA. [3] Molecular & Cellular Biology Graduate Program, University of Washington, Seattle, Washington, USA
| | - Guillermo A Orsi
- 1] Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA. [2] Centre National de la Recherche Scientifique UMR 218 and Institut Curie, Centre de Recherche, Paris, France
| | - Gabriel E Zentner
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA
| | - Kami Ahmad
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, Massachusetts, USA
| | - Steven Henikoff
- 1] Basic Sciences Division, Fred Hutchinson Cancer Research Center, Seattle, Washington, USA. [2] Howard Hughes Medical Institute, Seattle, Washington, USA
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10
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Dellino GI, Cittaro D, Piccioni R, Luzi L, Banfi S, Segalla S, Cesaroni M, Mendoza-Maldonado R, Giacca M, Pelicci PG. Genome-wide mapping of human DNA-replication origins: levels of transcription at ORC1 sites regulate origin selection and replication timing. Genome Res 2012. [PMID: 23187890 PMCID: PMC3530669 DOI: 10.1101/gr.142331.112] [Citation(s) in RCA: 120] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
We report the genome-wide mapping of ORC1 binding sites in mammals, by chromatin immunoprecipitation and parallel sequencing (ChIP-seq). ORC1 binding sites in HeLa cells were validated as active DNA replication origins (ORIs) using Repli-seq, a method that allows identification of ORI-containing regions by parallel sequencing of temporally ordered replicating DNA. ORC1 sites were universally associated with transcription start sites (TSSs) of coding or noncoding RNAs (ncRNAs). Transcription levels at the ORC1 sites directly correlated with replication timing, suggesting the existence of two classes of ORIs: those associated with moderate/high transcription levels (≥1 RNA copy/cell), firing in early S and mapping to the TSSs of coding RNAs; and those associated with low transcription levels (<1 RNA copy/cell), firing throughout the entire S and mapping to TSSs of ncRNAs. These findings are compatible with a scenario whereby TSS expression levels influence the efficiency of ORC1 recruitment at G1 and the probability of firing during S.
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Affiliation(s)
- Gaetano Ivan Dellino
- Department of Experimental Oncology, European Institute of Oncology, 20141 Milan, Italy.
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11
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Abstract
Epigenomics, the determination of epigenetic landscapes on a genome-wide scale, has progressed at an astounding rate over the past decade. Recent technological developments have enabled base-pair resolution of various epigenomic features, leading to new insights into epigenetic regulation.
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12
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Zentner GE, Henikoff S. Surveying the epigenomic landscape, one base at a time. Genome Biol 2012; 13:250. [PMID: 23088423 DOI: 10.1186/gb4051] [Citation(s) in RCA: 38] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Epigenomics, the determination of epigenetic landscapes on a genome-wide scale, has progressed at an astounding rate over the past decade. Recent technological developments have enabled base-pair resolution of various epigenomic features, leading to new insights into epigenetic regulation.
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13
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Petruk S, Sedkov Y, Johnston DM, Hodgson JW, Black KL, Kovermann SK, Beck S, Canaani E, Brock HW, Mazo A. TrxG and PcG proteins but not methylated histones remain associated with DNA through replication. Cell 2012; 150:922-33. [PMID: 22921915 DOI: 10.1016/j.cell.2012.06.046] [Citation(s) in RCA: 200] [Impact Index Per Article: 16.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2012] [Revised: 05/08/2012] [Accepted: 06/26/2012] [Indexed: 12/01/2022]
Abstract
Propagation of gene-expression patterns through the cell cycle requires the existence of an epigenetic mark that re-establishes the chromatin architecture of the parental cell in the daughter cells. We devised assays to determine which potential epigenetic marks associate with epigenetic maintenance elements during DNA replication in Drosophila embryos. Histone H3 trimethylated at lysines 4 or 27 is present during transcription but, surprisingly, is replaced by nonmethylated H3 following DNA replication. Methylated H3 is detected on DNA only in nuclei not in S phase. In contrast, the TrxG and PcG proteins Trithorax and Enhancer-of-Zeste, which are H3K4 and H3K27 methylases, and Polycomb continuously associate with their response elements on the newly replicated DNA. We suggest that histone modification enzymes may re-establish the histone code on newly assembled unmethylated histones and thus may act as epigenetic marks.
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Affiliation(s)
- Svetlana Petruk
- Department of Biochemistry and Molecular Biology and Kimmel Cancer Center, Thomas Jefferson University, Philadelphia, PA 19107, USA
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14
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Ishihara S, Varma R, Schwartz RH. A new fractionation assay, based on the size of formaldehyde-crosslinked, mildly sheared chromatin, delineates the chromatin structure at promoter regions. Nucleic Acids Res 2010; 38:e124. [PMID: 20371521 PMCID: PMC2887976 DOI: 10.1093/nar/gkq203] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023] Open
Abstract
To explore the higher order structure of transcribable chromatin in vivo, its local configuration was assessed through the accessibility of the chromatin to crosslinking with formaldehyde. The application of crosslinked and mildly sheared chromatin to sedimentation velocity centrifugation followed by size-fractionation of the DNA enabled us to biochemically distinguish between chromatin with heavily versus sparsely crosslinkable structures. The separated fractions showed a good correlation with gene expression profiles. Genes with poor crosslinking around the promoter region were actively transcribed, while transcripts were hardly detected from genes with extensive crosslinking in their promoter regions. For the inducible gene, Il2, the distribution of the promoter shifted in the gradient following T-cell receptor stimulation, consistent with a change in structure at this locus during activation. The kinetics of this switch preceded the chromatin change observed in a DNase I accessibility assay. Thus, this new chromatin fractionation technique has revealed a change in chromatin structure that has not been previously characterized.
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Affiliation(s)
- Satoru Ishihara
- Laboratory of Cellular and Molecular Immunology, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA.
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15
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Zhang Y, Oliver B. An evolutionary consequence of dosage compensation on Drosophila melanogaster female X-chromatin structure? BMC Genomics 2010; 11:6. [PMID: 20051121 PMCID: PMC2820458 DOI: 10.1186/1471-2164-11-6] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2009] [Accepted: 01/05/2010] [Indexed: 01/07/2023] Open
Abstract
Background X chromosomes are subject to dosage compensation in Drosophila males. Dosage compensation requires cis sequence features of the X chromosome that are present in both sexes by definition and trans acting factors that target chromatin modifying machinery to the X specifically in males. The evolution of this system could result in neutral X chromatin changes that will be apparent in females. Results We find that the general chromatin structure of female X chromosomes is distinct from autosomes. Additionally, specific histone marks associated with dosage compensation and active chromatin marks on the male X chromosome are also enriched on the X chromosomes of females, albeit to a lesser degree. Conclusions Our data indicate that X chromatin structure is fundamentally different from autosome structure in both sexes. We suggest that the differences between the X chromosomes and autosomes in females are a consequence of mechanisms that have evolved to ensure sufficient X chromosome expression in the soma of males.
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Affiliation(s)
- Yu Zhang
- Laboratory of Cellular and Developmental Biology, National Institute of Diabetes and Digestive and Kidney Diseases, National Institutes of Health, Bethesda, MD 20892-8028, USA.
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Beck S, Faradji F, Brock H, Peronnet F. Maintenance of Hox Gene Expression Patterns. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2010; 689:41-62. [DOI: 10.1007/978-1-4419-6673-5_3] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
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17
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Francis NJ, Follmer NE, Simon MD, Aghia G, Butler JD. Polycomb proteins remain bound to chromatin and DNA during DNA replication in vitro. Cell 2009; 137:110-22. [PMID: 19303136 PMCID: PMC2667909 DOI: 10.1016/j.cell.2009.02.017] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2008] [Revised: 10/22/2008] [Accepted: 02/02/2009] [Indexed: 01/11/2023]
Abstract
The transcriptional status of a gene can be maintained through multiple rounds of cell division during development. This epigenetic effect is believed to reflect heritable changes in chromatin folding and histone modifications or variants at target genes, but little is known about how these chromatin features are inherited through cell division. A particular challenge for maintaining transcription states is DNA replication, which disrupts or dilutes chromatin-associated proteins and histone modifications. PRC1-class Polycomb group protein complexes are essential for development and are thought to heritably silence transcription by altering chromatin folding and histone modifications. It is not known whether these complexes and their effects are maintained during DNA replication or subsequently re-established. We find that when PRC1-class Polycomb complex-bound chromatin or DNA is replicated in vitro, Polycomb complexes remain bound to replicated templates. Retention of Polycomb proteins through DNA replication may contribute to maintenance of transcriptional silencing through cell division.
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Affiliation(s)
- Nicole J Francis
- Department of Molecular and Cellular Biology, Harvard University, 7 Divinity Avenue, Cambridge, MA 02138, USA.
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18
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Kolodziej KE, Pourfarzad F, de Boer E, Krpic S, Grosveld F, Strouboulis J. Optimal use of tandem biotin and V5 tags in ChIP assays. BMC Mol Biol 2009; 10:6. [PMID: 19196479 PMCID: PMC2644297 DOI: 10.1186/1471-2199-10-6] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/20/2008] [Accepted: 02/05/2009] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Chromatin immunoprecipitation (ChIP) assays coupled to genome arrays (Chip-on-chip) or massive parallel sequencing (ChIP-seq) lead to the genome wide identification of binding sites of chromatin associated proteins. However, the highly variable quality of antibodies and the availability of epitopes in crosslinked chromatin can compromise genomic ChIP outcomes. Epitope tags have often been used as more reliable alternatives. In addition, we have employed protein in vivo biotinylation tagging as a very high affinity alternative to antibodies. In this paper we describe the optimization of biotinylation tagging for ChIP and its coupling to a known epitope tag in providing a reliable and efficient alternative to antibodies. RESULTS Using the biotin tagged erythroid transcription factor GATA-1 as example, we describe several optimization steps for the application of the high affinity biotin streptavidin system in ChIP. We find that the omission of SDS during sonication, the use of fish skin gelatin as blocking agent and choice of streptavidin beads can lead to significantly improved ChIP enrichments and lower background compared to antibodies. We also show that the V5 epitope tag performs equally well under the conditions worked out for streptavidin ChIP and that it may suffer less from the effects of formaldehyde crosslinking. CONCLUSION The combined use of the very high affinity biotin tag with the less sensitive to crosslinking V5 tag provides for a flexible ChIP platform with potential implications in ChIP sequencing outcomes.
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Affiliation(s)
- Katarzyna E Kolodziej
- Department of Cell Biology, Erasmus MC, Dr Molewaterplein 50, 3015GE Rotterdam, the Netherlands.
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19
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dMec: a novel Mi-2 chromatin remodelling complex involved in transcriptional repression. EMBO J 2009; 28:533-44. [PMID: 19165147 DOI: 10.1038/emboj.2009.3] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2008] [Accepted: 12/23/2008] [Indexed: 11/08/2022] Open
Abstract
The ATP-dependent chromatin remodeller Mi-2 functions as a transcriptional repressor and contributes to the suppression of cell fates during development in several model organisms. Mi-2 is the ATPase subunit of the conserved Nucleosome Remodeling and Deacetylation (NuRD) complex, and transcriptional repression by Mi-2 is thought to be dependent on its associated histone deacetylase. Here, we have purified a novel dMi-2 complex from Drosophila that is distinct from dNuRD. dMec (dMEP-1 complex) is composed of dMi-2 and dMEP-1. dMec is a nucleosome-stimulated ATPase that is expressed in embryos, larval tissues and adult flies. Surprisingly, dMec is far more abundant than dNuRD and constitutes the major dMi-2-containing complex. Both dNuRD and dMec associate with proneural genes of the achaete-scute complex. However, despite lacking a histone deacetylase subunit, only dMec contributes to the repression of proneural genes. These results reveal an unexpected complexity in the composition and function of Mi-2 complexes.
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20
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Henikoff S, Henikoff JG, Sakai A, Loeb GB, Ahmad K. Genome-wide profiling of salt fractions maps physical properties of chromatin. Genome Res 2008; 19:460-9. [PMID: 19088306 DOI: 10.1101/gr.087619.108] [Citation(s) in RCA: 189] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
We applied genome-wide profiling to successive salt-extracted fractions of micrococcal nuclease-treated Drosophila chromatin. Chromatin fractions extracted with 80 mM or 150 mM NaCl after digestion contain predominantly mononucleosomes and represent classical "active" chromatin. Profiles of these low-salt soluble fractions display phased nucleosomes over transcriptionally active genes that are locally depleted of histone H3.3 and correspond closely to profiles of histone H2Av (H2A.Z) and RNA polymerase II. This correspondence suggests that transcription can result in loss of H3.3+H2Av nucleosomes and generate low-salt soluble nucleosomes. Nearly quantitative recovery of chromatin is obtained with 600 mM NaCl; however, the remaining insoluble chromatin is enriched in actively transcribed regions. Salt-insoluble chromatin likely represents oligonucleosomes that are attached to large protein complexes. Both low-salt extracted and insoluble chromatin are rich in sequences that correspond to epigenetic regulatory elements genome-wide. The presence of active chromatin at both extremes of salt solubility suggests that these salt fractions capture bound and unbound intermediates in active processes, thus providing a simple, powerful strategy for mapping epigenome dynamics.
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Affiliation(s)
- Steven Henikoff
- Division of Basic Sciences, Fred Hutchinson Cancer Research Center, Seattle, Washington 98109-1024, USA.
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21
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Gupta S, Dennis J, Thurman RE, Kingston R, Stamatoyannopoulos JA, Noble WS. Predicting human nucleosome occupancy from primary sequence. PLoS Comput Biol 2008; 4:e1000134. [PMID: 18725940 PMCID: PMC2515632 DOI: 10.1371/journal.pcbi.1000134] [Citation(s) in RCA: 99] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/25/2008] [Accepted: 06/19/2008] [Indexed: 11/30/2022] Open
Abstract
Nucleosomes are the fundamental repeating unit of chromatin and comprise the structural building blocks of the living eukaryotic genome. Micrococcal nuclease (MNase) has long been used to delineate nucleosomal organization. Microarray-based nucleosome mapping experiments in yeast chromatin have revealed regularly-spaced translational phasing of nucleosomes. These data have been used to train computational models of sequence-directed nuclesosome positioning, which have identified ubiquitous strong intrinsic nucleosome positioning signals. Here, we successfully apply this approach to nucleosome positioning experiments from human chromatin. The predictions made by the human-trained and yeast-trained models are strongly correlated, suggesting a shared mechanism for sequence-based determination of nucleosome occupancy. In addition, we observed striking complementarity between classifiers trained on experimental data from weakly versus heavily digested MNase samples. In the former case, the resulting model accurately identifies nucleosome-forming sequences; in the latter, the classifier excels at identifying nucleosome-free regions. Using this model we are able to identify several characteristics of nucleosome-forming and nucleosome-disfavoring sequences. First, by combining results from each classifier applied de novo across the human ENCODE regions, the classifier reveals distinct sequence composition and periodicity features of nucleosome-forming and nucleosome-disfavoring sequences. Short runs of dinucleotide repeat appear as a hallmark of nucleosome-disfavoring sequences, while nucleosome-forming sequences contain short periodic runs of GC base pairs. Second, we show that nucleosome phasing is most frequently predicted flanking nucleosome-free regions. The results suggest that the major mechanism of nucleosome positioning in vivo is boundary-event-driven and affirm the classical statistical positioning theory of nucleosome organization. Inside the nucleus, DNA is wrapped into a complex molecular structure called chromatin, whose fundamental unit is ∼150 bp of DNA organized around the eight-histone protein complex known as the nucleosome. Understanding the local organization of nucleosomes is critical for understanding how chromatin impacts gene regulation. Here, we describe a computational model that predicts nucleosome placement from DNA sequence. We train the model using data derived from human cell lines, and we apply the model systematically to 1% of the human genome. We show that previously described models trained from yeast data correlate strongly with the human-trained model, suggesting a common mechanism for sequence-based determination of nucleosome occupancy. In addition, we observe a striking complementarity between models trained using data from weakly and strongly digested samples: one type of model recognizes nucleosome-free regions, whereas the other identifies well-positioned nucleosomes. Finally, our analysis of predicted nucleosome positions in the human genome allows us to identify common features of nucleosome-forming and inhibitory sequences. Overall, our results are consistent with the classical statistical positioning theory of nucleosome organization.
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Affiliation(s)
- Shobhit Gupta
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
| | - Jonathan Dennis
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - Robert E. Thurman
- Division of Medical Genetics, University of Washington, Seattle, Washington, United States of America
| | - Robert Kingston
- Department of Molecular Biology, Massachusetts General Hospital, Boston, Massachusetts, United States of America
| | - John A. Stamatoyannopoulos
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
- * E-mail: ;
| | - William Stafford Noble
- Department of Genome Sciences, University of Washington, Seattle, Washington, United States of America
- Department of Computer Science and Engineering, University of Washington, Seattle, Washington, United States of America
- * E-mail: ;
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22
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Abstract
Cellular memory is maintained at homeotic genes by cis-regulatory elements whose mechanism of action is unknown. We have examined chromatin at Drosophila homeotic gene clusters by measuring, at high resolution, levels of histone replacement and nucleosome occupancy. Homeotic gene clusters display conspicuous peaks of histone replacement at boundaries of cis-regulatory domains superimposed over broad regions of low replacement. Peaks of histone replacement closely correspond to nuclease-hypersensitive sites, binding sites for Polycomb and trithorax group proteins, and sites of nucleosome depletion. Our results suggest the existence of a continuous process that disrupts nucleosomes and maintains accessibility of cis-regulatory elements.
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Affiliation(s)
- Yoshiko Mito
- Basic Sciences Division, Fred Hutchinson Cancer Research Center, 1100 Fairview Avenue North, Seattle, WA 98109, USA
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23
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Schwartz YB, Pirrotta V. Polycomb silencing mechanisms and the management of genomic programmes. Nat Rev Genet 2007; 8:9-22. [PMID: 17173055 DOI: 10.1038/nrg1981] [Citation(s) in RCA: 653] [Impact Index Per Article: 38.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Polycomb group complexes, which are known to regulate homeotic genes, have now been found to control hundreds of other genes in mammals and insects. First believed to progressively assemble and package chromatin, they are now thought to be localized, but induce a methylation mark on histone H3 over a broad chromatin domain. Recent progress has changed our view of how these complexes are recruited, and how they affect chromatin and repress gene activity. Polycomb complexes function as global enforcers of epigenetically repressed states, balanced by an antagonistic state that is mediated by Trithorax. These epigenetic states must be reprogrammed when cells become committed to differentiation.
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Affiliation(s)
- Yuri B Schwartz
- Department of Molecular Biology and Biochemistry, Rutgers University, Nelson Laboratories, 604 Allison Road, Piscataway, New Jersey 08854, USA
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24
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Mohd-Sarip A, van der Knaap JA, Wyman C, Kanaar R, Schedl P, Verrijzer CP. Architecture of a Polycomb Nucleoprotein Complex. Mol Cell 2006; 24:91-100. [PMID: 17018295 DOI: 10.1016/j.molcel.2006.08.007] [Citation(s) in RCA: 64] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/10/2006] [Revised: 06/22/2006] [Accepted: 08/04/2006] [Indexed: 10/24/2022]
Abstract
Polycomb group (PcG) epigenetic silencing proteins act through cis-acting DNA sequences, named Polycomb response elements (PREs). Within PREs, Pleiohomeotic (PHO) binding sites and juxtaposed Pc binding elements (PBEs) function as an integrated DNA platform for the synergistic binding of PHO and the multisubunit Polycomb core complex (PCC). Here, we analyzed the architecture of the PHO/PCC/PRE nucleoprotein complex. DNase I footprinting revealed extensive contacts between PHO/PCC and the PRE. Scanning force microscopy (SFM) in combination with DNA topological assays suggested that PHO/PCC wraps the PRE DNA around its surface in a constrained negative supercoil. These features are difficult to reconcile with the simultaneous presence of nucleosomes at the PRE. Indeed, chromatin immunoprecipitations (ChIPs) and nuclease mapping demonstrated that PREs are nucleosome depleted in vivo. We discuss the implications of these findings for models explaining PRE function.
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Affiliation(s)
- Adone Mohd-Sarip
- Department of Biochemistry, Centre for Biomedical Genetics, Erasmus University Medical Center, P.O. Box 1738, 3000 DR Rotterdam, The Netherlands
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25
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Kahn TG, Schwartz YB, Dellino GI, Pirrotta V. Polycomb complexes and the propagation of the methylation mark at the Drosophila ubx gene. J Biol Chem 2006; 281:29064-75. [PMID: 16887811 DOI: 10.1074/jbc.m605430200] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
Polycomb group proteins are transcriptional repressors that control many developmental genes. The Polycomb group protein Enhancer of Zeste has been shown in vitro to methylate specifically lysine 27 and lysine 9 of histone H3 but the role of this modification in Polycomb silencing is unknown. We show that H3 trimethylated at lysine 27 is found on the entire Ubx gene silenced by Polycomb. However, Enhancer of Zeste and other Polycomb group proteins stay primarily localized at their response elements, which appear to be the least methylated parts of the silenced gene. Our results suggest that, contrary to the prevailing view, the Polycomb group proteins and methyltransferase complexes are recruited to the Polycomb response elements independently of histone methylation and then loop over to scan the entire region, methylating all accessible nucleosomes. We propose that the Polycomb chromodomain is required for the looping mechanism that spreads methylation over a broad domain, which in turn is required for the stability of the Polycomb group protein complex. Both the spread of methylation from the Polycomb response elements, and the silencing effect can be blocked by the gypsy insulator.
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Affiliation(s)
- Tatyana G Kahn
- Department of Molecular Biology and Biochemistry, Rutgers University, Piscataway, New Jersey 08854, USA
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26
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Lauri A, Xing S, Heidmann I, Saedler H, Zachgo S. The pollen-specific DEFH125 promoter from Antirrhinum is bound in vivo by the MADS-box proteins DEFICIENS and GLOBOSA. PLANTA 2006; 224:61-71. [PMID: 16374606 DOI: 10.1007/s00425-005-0193-9] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/23/2005] [Accepted: 11/21/2005] [Indexed: 05/05/2023]
Abstract
The Antirrhinum DEFH125 MADS-box protein is expressed in maturing pollen and thus likely participates in the regulation of pollen development. Here, we describe the characterization of a 2.5 kbp promoter fragment conferring pollen-specific GUS expression in Antirrhinum, as well as in the distantly related species Arabidopsis. Taking advantage of the higher sensitivity of the diphtheria toxin A-chain (DTA) reporter gene assay, onset of DEFH125 promoter activity could be defined to start at the late unicellular microspore stage. Stamen development in Antirrhinum is governed by the class B MADS-box genes DEFICIENS (DEF) and GLOBOSA (GLO). The respective proteins form a heterodimer and are expressed throughout stamens, except for microspores. Complementary expression patterns of DEFH125 and DEF/GLO during later stamen development tempted us to investigate whether the DEF/GLO heterodimer might bind the DEFH125 promoter and could thus be involved in repressing the DEFH125 expression. The ChIP technique was applied to investigate protein/DNA interactions occurring in vivo. We report the identification of a 200 bp DEFH125 promoter fragment that is in vivo bound by DEF and GLO proteins. This fragment contains a CArG-box motif, known to mediate DNA binding of MADS-box proteins. Implications for a likely function of DEF and GLO in the transcriptional control of DEFH125 are discussed.
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Affiliation(s)
- Andrea Lauri
- Max Planck Institute for Plant Breeding Research, 50829 Köln, Germany
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27
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Gilfillan GD, Straub T, de Wit E, Greil F, Lamm R, van Steensel B, Becker PB. Chromosome-wide gene-specific targeting of the Drosophila dosage compensation complex. Genes Dev 2006; 20:858-70. [PMID: 16547172 PMCID: PMC1475731 DOI: 10.1101/gad.1399406] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Abstract
The dosage compensation complex (DCC) of Drosophila melanogaster is capable of distinguishing the single male X from the other chromosomes in the nucleus. It selectively interacts in a discontinuous pattern with much of the X chromosome. How the DCC identifies and binds the X, including binding to the many genes that require dosage compensation, is currently unknown. To identify bound genes and attempt to isolate the targeting cues, we visualized male-specific lethal 1 (MSL1) protein binding along the X chromosome by combining chromatin immunoprecipitation with high-resolution microarrays. More than 700 binding regions for the DCC were observed, encompassing more than half the genes found on the X chromosome. In addition, several rare autosomal binding sites were identified. Essential genes are preferred targets, and genes binding high levels of DCC appear to experience the most compensation (i.e., greatest increase in expression). DCC binding clearly favors genes over intergenic regions, and binds most strongly to the 3' end of transcription units. Within the targeted genes, the DCC exhibits a strong preference for exons and coding sequences. Our results demonstrate gene-specific binding of the DCC, and identify several sequence elements that may partly direct its targeting.
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Affiliation(s)
- Gregor D Gilfillan
- Adolf-Butenandt-Institut, Molekularbiologie, Ludwig-Maximilians-Universität München, 80336 München, Germany
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28
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Straub T, Gilfillan GD, Maier VK, Becker PB. The Drosophila MSL complex activates the transcription of target genes. Genes Dev 2005; 19:2284-8. [PMID: 16204179 PMCID: PMC1240036 DOI: 10.1101/gad.1343105] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
The mechanism through which gene expression originating from the single male or the two female X chromosomes in Drosophila is adjusted to autosomal gene expression has remained controversial. According to the prevalent model, transcription of the male X is increased twofold by the male-specific-lethal (MSL) complex. However, a significant body of data supports an alternative model, whereby compensation involves a global repression of autosomal gene expression in males by sequestration and neutralization of an activator onto the X chromosome. In order to rigorously discriminate between these models we identified direct target genes for the MSL complex and quantified transcription in absolute terms after knockdown of MSL2. The results unequivocally document an approximate twofold activation of target genes by the MSL complex.
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Affiliation(s)
- Tobias Straub
- Adolf Butenandt-Institute, Molecular Biology Unit, Ludwig-Maximilians-University, 80336 Munich, Germany
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29
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Dorsett D, Eissenberg JC, Misulovin Z, Martens A, Redding B, McKim K. Effects of sister chromatid cohesion proteins on cut gene expression during wing development in Drosophila. Development 2005; 132:4743-53. [PMID: 16207752 PMCID: PMC1635493 DOI: 10.1242/dev.02064] [Citation(s) in RCA: 114] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
Abstract
The cohesin protein complex is a conserved structural component of chromosomes. Cohesin binds numerous sites along interphase chromosomes and is essential for sister chromatid cohesion and DNA repair. Here, we test the idea that cohesin also regulates gene expression. This idea arose from the finding that the Drosophila Nipped-B protein, a functional homolog of the yeast Scc2 factor that loads cohesin onto chromosomes, facilitates the transcriptional activation of certain genes by enhancers located many kilobases away from their promoters. We find that cohesin binds between a remote wing margin enhancer and the promoter at the cut locus in cultured cells, and that reducing the dosage of the Smc1 cohesin subunit increases cut expression in the developing wing margin. We also find that cut expression is increased by a unique pds5 gene mutation that reduces the binding of cohesin to chromosomes. On the basis of these results, we posit that cohesin inhibits long-range activation of the Drosophila cut gene, and that Nipped-B facilitates activation by regulating cohesin-chromosome binding. Such effects of cohesin on gene expression could be responsible for many of the developmental deficits that occur in Cornelia de Lange syndrome, which is caused by mutations in the human homolog of Nipped-B.
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Affiliation(s)
- Dale Dorsett
- Edward A. Doisy Department of Biochemistry and Molecular Biology, Saint Louis University School of Medicine, Saint Louis, MO 63104, USA.
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30
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Abstract
A large number of histone modifications has been implicated in the regulation of gene expression. Together, these modifications have the potential to form a complex combinatorial regulatory code. Genome-wide mapping approaches provide new opportunities to decipher this code, but they may suffer from systematic biases. Integration of datasets and improved technologies will provide the way forward.
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Affiliation(s)
- Fred van Leeuwen
- Netherlands Cancer Institute, Plesmanlaan 121,1066 CX Amsterdam, The Netherlands
| | - Bas van Steensel
- Netherlands Cancer Institute, Plesmanlaan 121,1066 CX Amsterdam, The Netherlands
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